* {
    margin: 0;
    padding: 0;
}
.box {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}
canvas {
    border: 1px solid #000;
    cursor: pointer;
}
/* contains seven box */
.queue {
    margin: 10px auto;
    margin-bottom: 0;
    height: 50px;
    background-color: #eee;
    overflow: hidden;
}
